Marine terpenes and terpenoids. X. Acid-catalyzed transannular cyclization of 11,12-epoxycembranolide.
作者:Masaru KOBAYASHI、Takuya HAMAGUCHI
DOI:10.1248/cpb.38.664
日期:——
Acid-catalyzed transannular cyclization of 11, 12-epoxycembranolide (1), isolated from the soft coral Sinularia mayi, was studied. The major product was the trans-fused bicyclo[8.4.0]tetradecene derivative 2, and the maximum yield was 89% with boron trifluoride in benzane at 0°C. When treated with p-toluenesulfonic acid in benzene at 55°C, 1 gave a bicyclo[9.3.0]tetradecene derivative 11 in 36% yield. Its immediate precursor was shown to be the allylic alcohol 4, which was converted to 11 on treatment with p-toluenesulfonic acid. The stereochemistries of the cyclization products indicated that the reaction takes place throught a conformation in which the dispositions of 11, 12- and 12, 13-bonds are crossed, with respect to the 7, 8- and 3, 4-double bonds, respectively.
研究了从软珊瑚 Sinularia mayi 中分离出的 11, 12-epoxycembranolide (1) 的酸催化环化反应。主要产物是反式融合的双环[8.4.0]十四烯衍生物 2,在 0°C 苯烷中使用三氟化硼的最高产率为 89%。在 55°C 时,用对甲苯磺酸在苯中处理 1,可得到双环[9.3.0]十四烯衍生物 11,收率为 36%。其直接前体为烯丙基醇 4,经对甲苯磺酸处理后转化为 11。环化产物的立体化学结构表明,反应是通过 11、12 和 12、13 键分别与 7、8 和 3、4 双键交叉的构象进行的。